JP2575751B2 - Image density control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention has both a density setting means capable of manual adjustment and a setting means for detecting a document image density and automatically obtaining an image of a constant density. The present invention relates to an image density control device of an image forming apparatus.

(B) Conventional technology Conventionally, there has been provided a control device for counting the number of copies for each copy density level set at the time of copying and determining an optimum density level from the result (for example, Japanese Patent Application Laid-Open No. 60-207156). And JP-A-61-77066). Further, there has been proposed a copying apparatus provided with setting means for detecting a document image density and setting a corresponding density level to obtain a copy image having a constant density (for example, see Japanese Patent Application Laid-Open No. 58-196552).

(C) Problems to be Solved by the Invention Incidentally, in the former, it is possible to set the density level suitable for the user's preference at the start of the copying operation, but in the latter, the density level is set in advance regardless of the degree of the document density. Although it is copied to the set predetermined density, the set density is not always adapted to the user's preference, and
Even if the level is appropriate for the user, there is a problem that the set density changes due to fatigue of the drum of the copying machine, contamination of the optical system, or fatigue of the developer.

The present invention has been made in view of such circumstances, and combines the former and the latter, and modifies the latter set density using the set density level information obtained from the former, thereby using the latter. An object of the present invention is to provide an image density control apparatus which automatically sets a density level preferable for an operator even when performing copying.

(D) Means for Solving the Problems FIG. 1 shows an image density control device according to the present invention. The image density control device 101 controls the image density of the image forming apparatus 103, and the image density level is manually set. A manual density setting means 102 for setting and obtaining an image of an arbitrary density, and a document image density detected by the detection means 106, and a density level corresponding to the document image density is automatically selected from a plurality of preset density levels. In the image forming apparatus 103 provided with the automatic density setting means 107 for obtaining an image of a constant density by switching means 109, the automatic density setting means 107 sets the density by using the manual density setting means 102, A totaling unit 104 that totals the image forming frequency for each density level set when forming a predetermined number of images every time an image is formed, and sets the density level at which the image forming frequency indicates the maximum as the optimum density level based on the totaling result. When there is a level difference between the determination means 105 for determining and the optimum density level obtained for each of the predetermined number of image formations, the density level selected corresponding to the original image density is corrected by the level difference and automatically established. A level determining unit 108 for setting a density level is provided.

(E) Operation In FIG. 1, the manual density setting means 102 sets an image density level by manual setting to obtain an image of an arbitrary density, and the automatic density setting means 107 sets the density based on the original image density. Select a level to obtain an image with a certain density.
The counting means 104 counts the image forming frequency for each density level which is set when the density is set using the manual density setting means 102 to form an image every time a predetermined number of images are formed. The density level indicating the highest image forming frequency is determined as the optimum density level from the result of the aggregation. When there is a level difference between the optimum density levels obtained for each of the predetermined number of image formations, the level determining means 108 corrects the density level selected corresponding to the document image density by the level difference and automatically sets the density level. Level.

(F) Embodiment Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. This does not limit the present invention.

FIG. 2 is a block diagram showing a main circuit of one embodiment of the present invention. Reference numeral 11 denotes a microcomputer having a built-in RAM, CPU, ROM and I / O port (hereinafter referred to as a microcomputer).
Is a keyboard that has various operation keys such as a copy key 12a, a copy number setting key 12b, a copy density setting key 12c, an automatic exposure key 12d, and is input to an I / O port of the microcomputer 11, and 13 is a nine-step A display device for displaying the density level from "0" to "8" of the indicator light 13a, an exposure control device 14 for controlling the exposure of the original document by receiving the output of the microcomputer 11, and a setting device 15 by various setting keys of the keyboard 12. A control device 16 controls various copying operations in accordance with the copy conditions to be performed, and a document density sensor 16 detects the document density and inputs it to the microcomputer 11.

The operation of such a control device will be described with reference to the flowcharts shown in FIGS. First, in FIG. 3, a power switch (not shown) is turned on (step 20).
1) When the copy conditions such as the number of copies and the original density are set by the keyboard 12 (step 202), the copy key 12a is turned on (step 203), and when the automatic exposure key 12d is not turned on (step 202), 203A), a copying operation corresponding to the set copying conditions is executed by the control device 15 and the exposure amount control device 14 (step 204, step 20).
Five). Incidentally, a subroutine (SUB1) shown in FIG. 4 is inserted between the step 203A and the step 204.
In FIG. 4, the density setting level set by the copy density setting key 12c and the number of copies to be copied at the set level are read (steps 206 and 207), and the user changes the setting level by the copy density setting key 12c. The number of copies is counted for each set level and stored in the RAM of the microcomputer 11 (step 208). In step 210, when the total number N of copies reaches a predetermined number (in this embodiment, N = 1000), a subroutine (SUB
1) ends.

In addition, a subroutine SUB2 shown in FIG. 5 is inserted after step 205 in the flowchart of FIG.
In FIG. 5, when the total number of copies reaches N = 1000 (step 209), the number of copies is read for each set level (step 210). The setting level L ₀ indicating the maximum number of copies of the read number of copies is selected (step 211). And this maximum value copy density level L ₀ corresponding to is copy density level of the copying machine is set to L ₀ (step 212) each counter clear while being stored in the RAM in the microcomputer 11 (step 213). Thus the optimal copy density level L ₀ for the next copying operation in the set automatically.

Next, in step 203A of FIG.
When d is on, only the optical system of the copying apparatus is driven by the control device 15 to perform document exposure (pre-scan) (step 301), and the document density is read by the document density sensor 16 (step 302). ). And beforehand ROM
From the table of the document density and the copy density level stored in the table, the copy density level L corresponding to the read document density.
Is read, and the exposure amount of the exposure amount control device 14 is set (step 303). At this time, if the optimum density L ₀ selected in step 213 has already been changed to L ₁ by the copying operation shown in step 204, the change amount ΔL = L ₁ −L ₀ is calculated (step S 213). 304), the change amount ΔL is added to the density level L set in step 303 (step 305), and the exposure amount of the exposure control device 14 is set based on the added copy density level, and the copying operation is performed. (Steps 306, 307).

In this manner, the amount of change in the optimum density level determined in the normal copying operation without automatic exposure is calculated, and the copy density level during automatic exposure is corrected accordingly. The density level is set to a desirable density for the user, and even if the copy density changes for some reason, the density is corrected to an appropriate copy density level.

In the above embodiment, the optimum density level is simply selected from the highest value of the frequency of use, but may be selected from a predetermined function using the frequency of use of each density level as a variable, or selected from a map of the predetermined frequency of use. You may make it.

(G) Effects of the Invention According to the present invention, a document image density is detected to obtain an image having a constant density suitable for the user's preference, and at the same time, the photoreceptor of the image forming apparatus is fatigued, the optical system is stained, and the development The change in image density due to the fatigue of the agent or the like is corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a block diagram showing a main part of an embodiment of the present invention, and FIGS. 3 to 5 explain the operation of the embodiment shown in FIG. FIG. 11 ... microcomputer, 12 ... keyboard, 12a ... copy key, 12b ... copy number setting key, 12c ... copy density setting key, 12d ... automatic exposure key, 13 ... display device, 13a ... display Light, 14: Exposure amount control device, 15: Various copy operation control devices, 16: Document density sensor.

Claims (1)

(57) [Claims] 1. A manual density setting means for setting an image density level by manual setting to obtain an image of an arbitrary density, detecting an original image density, and corresponding to the original image density from a plurality of preset density levels. In an image forming apparatus provided with a switchable automatic density setting means for automatically selecting a density level to be performed and obtaining an image of a constant density, the automatic density setting means sets the density using a manual density setting means and performs image formation. Totaling means for totalizing the image forming frequency for each density level set when a predetermined number of images are formed, and discriminating the density level indicating the highest image forming frequency from the totaling result as the optimum density level Means, when there is a level difference between the optimum density levels obtained for each of the predetermined number of image formations, the density level selected corresponding to the document image density is determined by the level difference. Correct image density control device characterized by comprising a level decision means for the automatic setting density level.